Residual stress and stress concentration effect of high strength steel built-up box T-joints

• The welding residual stress for HSS built-up box joints is studied.
• The SCF around the chord weld toe of HSS built-up box joints is studied.
• The effect of residual stress on the fatigue performance is discussed for built-up box joint.
• The residual stress and residual stress factor is compared for built-up box joints and plate-to-plate joints.

In this study, two built-up box T-joints made from high strength steel plates with yield stress equal to 690 MPa are investigated. The joints are fabricated with different welding procedures: one joint was welded at ambient temperature while the other one was welded at a preheating temperature of 100 °C. The residual stress distributions near the chord weld toe of both joints are measured by the ASTM hole-drilling method. The stress concentration factor distributions around the chord weld toe under axial loading, in-plane bending and out-of-plane bending are studied. To evaluate the effect of residual stress on the fatigue performance, the residual stress factor is put forward and discussed. After that, studies are carried out to compare the results from built-up box joints with the simpler plate-to-plate joints. Three comparisons are conducted: the first is to compare the welding residual stress magnitudes; the second is to compare residual stress factor at the mid-width of the plate-to-plate joints with that at the middle of the joint chord surface; and the third is to compare residual stress factor at the mid-width of the plate-to-plate joints with that at the corner of the joint where the maximum residual stress is found.